Process for separation and recovery of gold

ABSTRACT

Processes for and compositions utilized in the recovery of the gold content of gold containing substances by subjecting such substances -preferably in comminuted form- to the action of one of the following solvent system families: A. Aqueous gold solvation systems comprising primary or secondary mono-hydroxy alcohols, saccharides and/or carboxylic acids and iodine or bromine. B. Aqueous iodine-containing gold solvation systems comprising primary or secondary monohydroxy alcohols and ditri- and polyhydric alcohols in the place of or in addition to saccharides and carboxylic acids. C. Essentially non-aqueous gold solvating systems comprising secondary alcohols and iodine. Solvation of the gold occurs during agitation and heating of the slurry. The gold contents are removed from the gold pregnant solution by displacement onto a non-noble metal surface. The solid gold containing residue is treated with sufficient aqueous hydroxide solution to convert excess non-noble metal into its water-soluble salt. The remaining insoluble material containing the gold metal recovered is rinsed to remove any remaining unreacted alkali and the soluble salts and is then digested with concentrated sulfuric acid to dissolve any remaining acid soluble impurities, the remaining acid insoluble residue is rinsed, dried and comprises substantially pure gold metal.

[451 Dec. 11, 1973 PROCESS FOR SEPARATION AND RECOVERY OF GOLD [75]Inventor: Harold W. Wilson, El Paso, Tex.

[73] Assignee: The Golden Cycle Corporation, Victor, C010.

[22] Filed: Feb. 12, 1970 [21] Appl. No.: 11,011

[52] US. Cl 75/101 R, 75/102, 75/109, 75/118 [51] Int. Cl. C22b 3/00,C22b 11/04 [58] Field of Search 75/118, 121, 101 R, 75/101 BE, 102, 109,83, 100; 23/312 R; 260/429 J [56] References Cited UNITED STATES PATENTS2,304,823 12/1942 Harrison 75/118 682,061 9/1901 Grollet.... 75/1023,511,645 5/1970 Goni 75/101 R 2,239,519 4/1941 Gurwood 75/118 X3,625,674 12/1971 Jacobs 75/118 X Primary Examiner-G. T. OzakiAttorney-Clarence A. OBrien and Harvey 13. Jacobson [57] ABSTRACTProcesses for and compositions utilized in the recovery of the goldcontent of gold containing substances by subjecting such substancespreferably in comminuted formto the action of one of the following solvent system families:

A. Aqueous gold solvation systems comprising primary or secondarymono-hydroxy alcohols, saccharides and/or carboxylic acids and iodine orbromine.

B. Aqueous iodine-containing gold solvation systems comprising primaryor secondary monohydroxy alcohols and ditriand polyhydric alcohols inthe place of or in addition to saccharides and carboxylic acids.

C. Essentially non-aqueous gold solvating systems comprising secondaryalcohols and iodine.

Solvation of the gold occurs during agitation and heating of the slurry.The gold contents are removed from the gold pregnant solution bydisplacement onto a non-noble metal surface. The solid gold containingresidue is treated with sufficient aqueous hydroxide solution to convertexcess non-noble metal into its water-soluble salt. The remaininginsoluble material containing the gold metal recovered is rinsed toremove any remaining unreacted alkali and the soluble salts and is thendigested with concentrated sulfuric acid to dissolve any remaining acidsoluble impurities, the remaining acid insoluble residue is rinsed,dried and comprises substantially pure gold metal.

18 Claims, No Drawings PROCESS FOR SEPARATION AND RECOVERY OF GOLD U.S.Pat. No. 3,576,620 Application Serial No. 727,666, filed May 8, 1968,sets forth a substantially non-aqueous process for separation andrecovery of noble metals, particularly gold, platinum and metals of theplatinum group from materials containing the same. The process comprisessubjecting a slurry obtained by admixing particulate, preferably finelydivided, dry material containing noble metals with an iodinecontainingketonic solvent, to heating and agitation to effect the solvation andthus the separation of the noble metals from the other constituents ofthe material. The liquid phase so derived is acidified and heated toeffect volatilization of the iodine by decomposition of iodinenoblemetal compounds together with attendant liberation, i.e., precipitationof elemental noble metals due to the decomposition of organic andinorganic noble metal containing compounds. Alternatively, the aboveapplication teaches that noble metals may be separated and recoveredfrom materials containing the same by first dissolving noble metals withaqua regia to transform the noble metals present into their respectivechloride salts which are then subjected to a ketonic solvent which neednot contain iodine. The resultant mixture is then heated to removeexcess ketonic material leaving an organic resinous residue containingnoble metal inner complex compounds. Acidification and heating result inthe decomposition of the organic matter and solvation of the non-noblemetal components of the residue, leaving a final residue comprisingessentially pure elemental noble metals.

in U.S. Pat. No. 3,709,681 an improvement is disclosed over thecompositions and processes to be utilized in the recovery of gold andother noble metals over those set forth in U.S. Pat. No. 3,576,620. Theimprovements set forth in that application reside in a novel metalsolvation process utilizing in its preferred embodiment diacetonealcohol solvent containing not only dissolved iodine, but also aquantity of water, iodides of non-noble metals and acetic acid to yielda solution containing noble metal inner complex ketonic compounds. Thenoble metals are then recovered in essentially pure state in the form'of a sheet or foil by a displacement process involving aluminum foil asset forth in detail in said application.

The present invention relates to compositions and processes ofsolvation, isolation and recovery of gold in the metallic state from anysubstance known to contain it. Unlike the applications referred tohereinabove, this invention relates primarily to the recovery of goldand is not particularly concerned with the recovery of any other noblemetals. It is an object of this invention to provide new compositionsfor dissolving and thereafter recovering gold from substances containingsame.

It is another object of this invention to devise new processes fordissolving gold and gold metal alloys.

Another object of this invention is to permit the recovery of dissolvedgold in pure or relatively pure form as elemental gold.

Another object of this invention is to increase the rate of dissolutionof gold.

Another object of this invention is to substantially increase thepercentage of gold which can be dissolved and therefore recovered fromthe gold contents of any gold containing material.

Another object of this invention is to permit the recovery from whatevermaterial may contain the same, gold located within that material,whether the gold be present as a major constituent or whether it bepresent in no more than trace quantities.

Further objects and aspects of this invention will become apparent inthe following discussion.

The present invention contemplates the use of one of the followingfamilies of solvent systems for the solvation and recovery of gold:

A. Aqueous Gold Solvation Systems Comprising Primary or SecondaryMono-hydroxy Alcohols, Saccharides and/or Carboxylic Acids and Iodine orBromine These new compositions of matter are liquids consistingessentially of combinations of saccharides and/or hydroxy carboxylicacids, ethyl alcohol (C l-l Ol-l), iodine or bromine, and water.

Since alcohol (ethanol) and water are the principal ingredients of thisnew family of compositions of matter utilized as gold solvating agents,alcoholic beverages such as wine, brandy, rum, whiskey, gin and mixturesthereof would be quite suitable as the sources of both the alcohol andwater required in the preparation of the solvents of this invention.However, mainly for reasons of economy, the preferred embodiment of thisinvention involves the use of industrial grade denatured ethanol, suchas, for example SDA Formula No. l. gallons of ethanol to which have beenadded 5 gallons of wood alcohol) with water added as required, as willbe explained below. It may be pointed out that alcoholic beverages alsocontain saccharides, carboxylic acids, and higher alcohols in additionto their ethanol and water content. Alcoholic beverages may be usedwithout modification or they may be fortified with ethanol, e.g., by theaddition of grain alcohol. Denatured (wood alcohol-containing)industrial ethanol provides excellent gold metal and gold metal alloysolvents suitable for use in practicing this invention.

The saccharide component of the solvent compositions of this inventionmay be selected from either mono-, di-, or polysaccharides such as, forexample, glucose, sucrose (cane or beet sugars),and starch. The hydroxycarboxylic acid component which may be utilized in addition to orinstead of the saccharide component may be selected from mono-, di-, andpolyhydroxy, monocarboxylic or dicarboxylic acids, such as, for example,glycollic, tartaric, fumaric, malic, succinic, maleic, and gluconicacids. All are suitable and may be satisfactorily employed in thepreparation of the disclosed solvents for gold.

The halogen component of the gold dissolving compositions hereindisclosed may be either elemental iodine or elemental bromine. However,elemental iodine is deemed to be a preferred embodiment because it hasbeen established that the presence of iodine greatly accelerates thenecessary inversion of sucrose, the preferred saccharide. Additionally,its presence greatly enhances concomitant reactions of halogenation,dehydration, rehydration, hydrogenation, condensation, oxidation, andreduction thus resulting in a superior solvent for gold metal. Wheresaccharides other than sucrose, e.g., invert sugar are used, with orwithout hydroxy carboxylic acids (e.g., mono-, di-, or polyhydroxymonocarboxylic or di-carboxylic acids), either halogen may be used toprovide equally satisfactory gold metal solvents.

The compositions of this invention overcome in a novel and unobviousmanner the difficulty inherent in the prior art. Thus, it has previouslybeen disclosed that either iodine or bromine in the presence of theirhalide salts (such as potassium and sodium iodide) are capable ofreacting with metallic gold to form gold halide salts. It should benoted that halide salts as noted above are not used nor is their userecommended in this invention since studies have shown that theirpresence in the noted new compositions of matter utilized as solventsfor gold does not enhance the solvation of gold metal but actuallyhinders it.

It is also known that the gold content of aqueous gold halide saltsystems can be readily reduced to the metallic state in the presence ofsugars (saccharides) or dicarboxylic acids (such as oxalic acid). As apractical matter, the tremendous instability of gold halide salts andthe strong tendency of the gold ions of such salts in aqueous medium tobecome reduced to their elemental state contraindicates the using of acomposition of matter such as above described as solvents for goldmetal.

The mechanism for the solvation of gold utilizing the new compositionsof matter disclosed herein may be more readily understood by referenceto the series of equations set forth below relating to the preferredembodiment namely the use of a combination of sucrose, elemental iodine,ethyl alcohol, and water:

sucrose ulucusc fructose HI H1O C H OH hydration 2. (3 11, 0,

glucose +Hz0 3. C l-L 0 glucose H202 izluconlc acid succlnlc ZlCldacclaldehyde The above equations illustrate a few definable reactionswhich take place within the system, in addition to many others.Additionally, the elemental halogen and the hydrogen halide acid (e.g.,HI or I-IBr) present in the system react across the double bonds of thesystems unsaturated organic acids and also displace the hydroxyl groupsof the hydroxy carboxylic acids present. This results in the formationof halogenated hydroxylated and halogenated non-hydroxylated monoanddi-carboxylic acid compounds. The foregoing com-- pounds areinstrumental in converting gold metal into its iodide form (Aul), aninorganic salt of gold soluble in an ethanol-water system as well asinto aurousiodinecarboxylic acid compounds (organic salts of gold)soluble in the ethanol-water systems of this process, thus effectivelyaccomplishing the solvation of the gold metal. The following equationsillustrate the reactions which result in the formation of thehalogenated compounds capable of dissolving gold to an acceptable degreeof completeness and at an acceptable rate:

dl-lodo-succlnlc aclt runaw- :mld HOOC-C(CZ I:l (I) l;l(l)-COOH+H O Thefollowing table demonstrates the indispensable nature of each of thenoted system components in achieving the solvation of gold. For purposesof comparison, the quantity of gold exposed to solvation, the

4. C H O HOOC-CH(OI-I)CH(OH)COOH 1mm 201 1 1mm arld particle size andall other relevant conditions were kept -3535511 3 H2O constant:

TABLE.- GOLD METAL DISSOLUTION WITH USE OF VARIOUS SOLVENT SYSTEMSSaccharide carboxylic acid Alcohol Gold metal Solvent Iodine, Water,dissolved. system kind gms. kind gms. ems. source ml. ml. mgs.

1 sucrose 30 6.5 2.. invert sugar... 25 205 3.. 25 0.5 4.. tartaricacid. 30 227 5.. 25 205 6.. 25 20.5 7.. 30 12560 8.. 30 9973 9.. 4520835 10. l5 whiskey I00 pf... 5277 ll... 20 brandy pf. 5364 12... 20grain alc. p 9880 13 20 port wine 20%... 400 1002 1 5 0 o 200 4 sucrose2 grain ale 190 M n 3367 15 invert sugar............ 20 20 rum 80 pf 4004716 s. crucuo cu coou 7 nugllrg g-Id Referring to the above table, itis readily apparent that the amounts of gold metal dissolved varied fromalmost none in a system limited to elemental iodine and water to only6.5 mgs. in the foregoing system additionally containing sucrose. Thesubstitution of inverted sugar for sucrose increased the amount ofdissolved gold to 205 mgs. An ethanol-iodine system was capable ofdissolving 205 mgs. of gold. The substitution of tartaric acid for theinvert sugar in the presence of water and halogen resulted indissolution of only 227 mgs. of gold. In contrast therewith the use ofslightly more iodine and the use of ethanol in conjunction with tartaricacid in the dissolving medium results in the dissolution of 12,560 mgs.of gold. Further inspection of the table shows that the use of alcoholicbeverages or grain alcohol (190 proof) in conjunction with sucrose (orinvert sugar) and with elemental iodine resulted in the dissolution ofremarkable amounts of gold metal. Port wine typically containsapproximately 2-3 percent sugar and 20 percent ethyl alcohol as naturalconstituents. A port wine having the described constituents was used,together with additional sucrose and ethanol, as a gold solvationmedium. This composition dissolved three times the amount of gold ascompared with the amount of gold dissolved by the same kind of port winecontaining the same amount of elemental iodine but not fortitied withadditional sugar or ethanol. A composition comprising 1 pint of alcohol(95 percent C H OH 190 proof), 0.1 pounds of table sugar (sucrose), and0.1 pound dissolved elemental iodine was capable of dissolving 20,835mgs. or 0.67 troy ounces of gold metal.

Ethanol is the most effective of the primary or secondary alcoholsutilized in the practice of this invention. Thus, while experimentalstudies have indicated that primary and secondary alcohols such as forexample, methanol and isopropanol may be used in substitution forethanol in conjunction with the presence of elemental halogen and thesaccharides or carboxylic acids, the resulting degree of gold metalsolvation is limited in amount as compared with the amount dissolvedwherein ethanol is used. For example the substitution of methanol forethanol -all other conditions being kept constantresulted in thedissolution of only 33 mgs. of the gold sample exposed. isopropanolresulted in only 27 mgs. of gold metal becoming dissolved. In comparisontherewith the use of ethanol in the identical system resulted in thedissolution of 2,062 mgs. of gold metal under the same conditions.

Additional studies have shown that in all ranges of proportion, systemscontaining all three of the noted principal constituents (i.e.,saccharides and/or carboxylic acids, elemental halogens and ethanol),such systems were capable of dissolving many times more gold metal andgold metal alloys than it was possible to dissolve under the sameconditions by using any combination of just two of the three namedcomponents. Experiments have also established that the use of sucrose orinverted sugar instead. of singular carboxylic acids in preparing thesolvation systems of this invention produced superior results. It isthought that this is attributable to the reactions of sucrose, orinverted sugar with the elemental halogen and hydrogen halide acid whichresult in the production of a multiplicity of hydroxy carboxylic acidswhich are in turn capable of reacting with gold to produce organic saltsof gold soluble in the ethanol and water present in the system. Theabove findings were corroborated by using alcoholic beverages, e.g.,port wines as the sources of ethanol and sugar, and using such sugarinstead of the singular carboxylic acids. 7

The presence of water in the new compositions for the solvation of goldnot only enhances the overall reactivities between the three principalcomponents as well as the reactivities of the products of theirreactions with gold exposed to such a system, but is also necessary forthe formation of hydrogen halide acid and the attendant formation of thewater-ethanol soluble inorganic salts of gold, e.g., aurous iodide orbromide as the case may be.

As a preferred embodiment the optimum solvent system should consist ofan amount of ethanol sufficient to dissolve the amount of elementalhalogen used. For instance, 12.5 ml. of ethanol are required to dissolve1 gram of 1 Water must be introduced into the system in an amountsufficient to dissolve the amount of the saccharide or carboxylic acidsintroduced into the sys tem. For example, 0.5 ml of water are requiredto dissolve one gram of sucrose. The total amount of elemental halogenshould be slightly in excess of the stoichiometric requirements to formgold halide as well as the base metal halides of any base metals whichmay be present. The amount of saccharides or carboxylic acids usedshould be proportional to the amount of halogen introduced into thesystem. The range of proportions expressed in parts by weight ofsaccharide or carboxylic acid to halogen should generally be 1:4 up to1:1. In any event the solvent system should contain no insol uble matterwhatsoever. In accordance with this invention, solvent preparation andgold solvation can occur simultaneously or sequentially.

A quantity of gold metal having a particle size of 60 mesh (U.S. std.sieve sized) was placed into a flask equipped with a water cooledcondenser. Equal weights of sucrose and elemental iodine were added tothe flask containing the gold particles, followed by the addition ofindustrial grade ethyl alcohol and water. The flask and its contentswere shaken until the sugar and iodine were observed to have dissolved.With the condenser in place, the contents were heated under refluxconditions to a temperature in the vicinity of the boiling point of themixture and maintained in this heated state until it was evident fromvisual observation that no undissolved gold particles remained in theflask.

Where the gold containing substance to be processed is a gold bearingore or gold mineralized substance it is preferable to first prepare thesolvent by combining the required amounts of ingredients and heatingunder reflux conditions as noted above until the condensate is colorlessor nearly so (light yellow) indicating that the iodine or other halogenemployed has combined chemically with the solution rendering thesolution ready for use as a gold solvent. In the case of high contentgold mineralized substances, the solvent as prepared above may be usedas such to recover gold from mineralized substances having such highgold content, or it may be diluted with increasing amounts of water toprocess ores with decreasing gold content, as illustrated hereinafter.Thus, in cases of materials having a relatively low gold content, e.g.,ores containing gold in amounts between 0.1 to 0.5 troy ounces of goldper ton, the original solvent (concentrate) may be diluted so as tobecome predominantly aqueous (99.9% H 0), and contain in the range of100 to 1,000 parts per million of the concentrated" solvent. Forexample: a solvent prepared by use of 5 grams of sucrose, 5 grams ofelemental iodine, ml. of denatured ethyl alcohol, and 24 ml. of water,all refluxed as noted above will result in a concentrated solvent whereeach 1 ml. will contain approximately 0.05 grams of iodine in chemicalcombination with carboxylic acids and ethyl alcohol. One ml. of thissolution added to and mixed with one liter of water provides a secondarysolvent solution. 200 ml. of this secondary solvent system were combinedand intimately mixed at ambient temperature with 200 grams of comminutedgold bearing ore having a gold content of 0.1 to 1.0 troy ounces of goldper ton. After a 15 to 20 minute mixing period the liquid portioncontaining the dissolved gold (and base metals) was mechanicallyseparated from the insoluble solid matter. The insoluble solid matterwas then washed free of entrapped gold pregnant liquid with either waterdiluted methanol or ethanol (1 part of alcohol to 4'6 parts of water)and the washings were combined with the originally separated goldpregnant liquid to be processed for the isolation and recovery of thegold contained therein by any suitable process. The preferred methodinvolves the displacement of gold utilizing a base metal such asaluminum, copper, iron and zinc as disclosed in U.S. Pat. No. 3,709,681.

The nature of the material to be treated to remove its gold content mustbe considered in formulating the amounts and relative proportions ofsystem constituents to be used. Thus, when it is desired to dissolvegold metal alloys or to treat ores of gold mineralized substances knownto contain base metals in addition to gold, the contents of such basemetals present must be taken into consideration relative to the amountof halogen employed in the dissolving agent since such base metals arelikewise dissolved by these new compositions of matter used as goldsolvents. For example, dissolving a gold metal alloy known to contain90% gold, 5% silver and 5% copper, the solvent employed must contain atleast sufficient halogen to meet the stoichiometric requirements toconvert all three metals into their mono-valent halide salts. A slightexcess of the halogen employed, -preferably approximately to percentmore than is known to be required stoichiometricallywill not only assurecomplete dissolution but will also greatly enhance the time rate ofdissolution of the alloy. In addition, such a slight excess of halogenwill materially assist in helping retain nonorganic gold compounds insolution until it is desired to convert them to elemental gold. B.Aqueous Iodine-containing Gold Solvation Systems Comprising Primary orSecondary Monohydroxy Alcohols and Di-tri and Polyhdric Alcohols in thePlace of or in Addition to Saccharides and Carboxylic Acids Goldsolvents of the above-described type differ from those disclosed in theimmediately preceding section of this specification in that ditri-, andpolyhydric alcohols are utilized in the place of or in addition to thesaccharides and carboxylic acids. In this way it is possible to increasealmost three-fold the time rate of dissolution of the gold metal ascompared to the solvent systems not containing di-, triand polyhydricalcohols.

The liquid primary or secondary mono-hydroxy alcohols useful inpreparing solvent systems of this type include, for example; methanol,ethanol, isopropanol, butanol and pentanol, or mixtures of same. Thedi-, tri-, and polyhydric alcohols useful in practicing this inventioninclude, for example: ethylene and/or propylene glycols, glycerine,erythritol and sorbitol or mixtures thereof, in place of or in additionto the Saccharides andcarboxylic acidsas previously disclosed. Theelemental halogen used in the preparation of solvents of this type maybe either iodine or bromine.

The element iodine (I is the preferred halogen in the preparation ofthis type of solvent system. One significant reason for the preferenceis based on the physical properties of iodine, including the fact thatit is easily handled. In addition the preference is based on thechemical properties of its compounds which exist in the solvent systemat one time or another. These iodine compounds include halogen acidssuch as HI and H10 alkyl halides such as C H I, alkyl halogenated acidssuch as CH ICOOH, and alkyl halogenated aldehydes such as CH ICHO. Theforegoing are among the most reactive of halogenated compounds andhighly effective gold solvents.

The solvent systems of this type are prepared by combining all of theingredients and heating the resultant liquid under reflux conditionsuntil colored vapors have nearly disappeared. During the heating step,the system is characterized by the following principal reactions, all ofwhich occur to some degree depending upon the nature and the amount ofingredients used:

momriodulartarlc nun hydroxy acetone coon f l CH OH ulycollic ziCill CHOCH +%o;

CH OH; CH OH ulycolllc aldehyde COOH +aof CHO l3. (IZH OH ethyleneRlycol CH0 CH0 l 2 l CH0 CH0 slyoxnl ulyuxallc acid V cHpH cHn H Theresultant solution is highly acidic (pH about 2.0) and may be used as agold solvating agent as such. In another embodiment of this inventionaluminum foil is added to the system and the liquid contents are heatedto their boiling point or nearly so and held at that temperature untilsuch time as the foam appears to be white or nearly so and the color ofthe liquid has changed from deeper red to a transparent grey-green coloror until it becomesa nearlycolorless transparent liquid. After this isobserved, the unreacted portion of the aluminum foil used ismechanically removed from the liquid and discarded. The introduction ofaluminum metal under the above conditions has the effect of initiating aseries of reduction and catalytic reactions which result in the almosttotal consumption of uncombined water and liberation of hydrogen. Thechemistry of the system is characterized by the following equations:

CH COOH CH ICOOH 2H CH CHO CH ICHO 2H O 20. 2AlI 3ROH Al (ORI) 3H] 21.2A1 6ROH 2A1(OR) 3H alumlnum alcnholate Al (OH) C H O AI(OH)C H O 2H Omalls and aluminumallc acld dlalkyl monualkyl scsquilodide diiudidedlhydroxy acetone Q to. EL. a. a. 31. CH COOH 2H] CH CHO +1 H O Theacidity of the solution resulting from the introduction of aluminumvaries from pH 2.0 to pH 1.5, i.e., either slightly less acidic orslightly more acidic than it was prior to the introduction of thealuminum.

After the aluginum has reacted with the solution, additional elementalhalogen is then added to the prepared liquid containing the dissolvedaluminum and the mixture is subjected to the action of moderate heat.The amount of additional halogen introduced may be roughly on the orderof the amount originally introduced. The newly introduced halogen isprimarily consumed in halogenation of the organic comounds pres- CH OHally] alcohol ent along with some esterification. Much of the waterremaining is consumed in a combination of oxidation and halogenationreactions while part of the halogen introduced remains in its elemental(chemically uncombined) form. The following reactions are considered tobe illustrative of many of the reactions possible in this step:

32. CH ICHO I CHLCHO H1 34. 2(HOCH --CH=CH +2HIO CHOH +CHI 37. acu cno+1 H210 RCHZCOOH 2H1 3s. Rcrncooii 1 RCHICOOH HI 39. RCHICOOH R'OHRCHICOOR H- 40. (CH (CH COO) Al 31 3(CH (CH COOI) A11 41. CH =CHOH +1 CHI CHOl 42. RCH CHO +1 RCHICHO HI 43. ROH HI RI H O The total amounts ofelemental halogen introduced in preparing solvents must be such inamount that there will be sufficient halogen to meet the stoichiometricrequirements of all reactable metals and compounds present in substancesto be processed to enable the conversion of such metals to their highestvalence states as metallic halides while at the same time leaving someuncombinedhalogen in solution. In the case of processing gold metalitself there must be sufficient elemental halogen present to meet thestoichiometric requirements shown below:

44. 2 Au 6H1 1 ZH AuL,

If insufficient halogen is present to satisfy the above, a part of thegold metal previously dissolved will revert to metallic state as shownbelow:

45. H Aul Aul 3H1 46. 3 AuI Aul 2Au The properly halogenated highlyacidic resultant product is now ready for use as a highly concentratedgold metal solvent which may be used as such or which may be dilutedwith water. Water dilution to an extent as great as 1 part of solventper 100,000 parts of water by volume will provide a most suitableproduct for dissolving metallic gold. Several of the principal reactionsinvolved with use of the prepared solvents for dissolving gold metal areillustrated below:

I: catalyst 52. Au 3R I R AuI RAuI 53. 2Au RCHlCHO HI 2Au] RCH CHO 54.2Au RCHICOOH Hl 2Aul RCH COOH 55. 2Au Hl HIO 2Aul H 0 56. Au! 1 Aul 57.2Aul 2H1 2Aul 3L H 58. Aul 3H[ H5Aul 59. 6Au Aul 3HIO 6Aul H AuO 60. HAuQ 3H] Aul 3H O Among the advantages which accrue by reason of the useof this process is the fact that it permits ultimate production ofmixtures of highly compatible halogenated organic and inorganiccompounds all of which act synergistically and in concert in a rapid andvigorous manner in dissolving gold metal to form combinations of goldorganic and gold inorganic compounds all of which are highly soluble inthe medium in which they were formed. Additionally all of the goldcompounds formed are of such nature that their content of gold ions canbe easily converted to elemental gold which can then be mechanicallyisolated and recovered by simple means to leave residual gold-freeliquid compounds which can be re-halogenated for re-use as gold metalsolvents having the same gold metal dissolving capacities as theypossessed originally. This regeneration" is possible simply because whenthe gold metal dissolves in the original solvent it acts in the samemanminus percent of the total volume of the solvent. The amount ofhalogen is regulated by introducing an amount sufficient to meet thepreviously noted stoi chiometric requirement to dissolve the gold andother ner as the metallic aluminum foil acted when used in 5 metals ofthe material to be processed or can be in expreparation of the saidoriginal solvent prior to its use cess of such requirements providingthe excess halogen as a gold metal solvent. that is in the system iscapable of remaining dissolved The gold pregnant solution is then freedof its gold in said system. The amounts of saccharides, carboxyliccontent, preferably by introducing metallic aluminum id polyhydricalcohol and related compounds as foil rather than powdered or granularmetallic alumipreviously enumerated must b o letely soluble in num intosuch solution for the purpose of converting its the stem, St dies haveshown optimal amount by content of ionic gold into elemental gold topermit the weight to equal to or be slightly greater (10 percent tomechanical removal of the gold as insoluble metal in 20 t) h th t t l ntb ight of h l the form of gold foil in one piece or in several easilyregen s d d are between 20 percent to 30 percent b coverable smallpieces. The principal reaction mechai ht f th t t l weight f the ombintion of all innism involved in this step are those of replacement andgredients u ed to produce the final undiluted solvent displacementpredominantly as shown below: system. The amounts of primary and/orsecondary monohydroxy alcohols shown to be optimal lie in the 1 4A 613Aul 2A1 3 u range of 70 percent to 85 percent of the total liquid vol-)s A1 M All umes of the finished product either prepared for use as isuch or prepared for use with water dilution. The A 1 RCH CHO+A1 OH +A63 RCH P T 2 )3 u ambunts of metallic alummum metal foil (household 4 6H3 g l 9 6Au type) found to be optimal forboth the decolorization stepand for the gold displacement step are not critical AU(OR)3 AKOR) Auother than there should be sufficient metallic foil pres- 66. Au (OR) l2A1 Al (OR) I 2Au ent to achieve the required results as notedpreviously. 67' CHAU CH3 Studies have shown that one gram of householdaluminum foil will decolorize solvent solutions containing 6cm 2 2 i+about 20 grams of dissolved halogen and will displace CHZOH CHZOHapproximately one-third troy ounce of metallic gold from the goldpregnant solutions obtained to leave ap- COOH CH0 proximately 25 to 50percent of the aluminum metal I +Al+9H 3 All;,+3Au+9H CHAui o foiloriginally introduced as residual metal after the completion of eitherof the main steps of this process. 3H2 69. 6CHAulCHQ+2Al 6CH CHO+2All+6Au The following 15 a group of examples presenting in tabular form thevarious quantitative aspects of this inln formulating the amounts andproportions of the vention. In each instance the amount of gold metalexvarious constituents and reactants in the practice of posed tosolvation was 10.00000 grams of 99.99 perthis invention the requirementsinclude that the cent pure gold with paritcle sizes ranging from 0.125amount of water employed at the onset of solvent prepinch to 0.010 inch.In each instance the gold was exaration should be in the range of 10percent plus or posed to solvation for a period of 1 hour.

TABLE I1 Alumi- AulN troy num con- Gold ozs. dis- Saccharides,carboxylic acids, and Halogen sumed metal dissolvable polyhydricalcohols used, kind & Monohydroxy alcohol used, kind & Water used,(decolor.) solved. per pint of weight in gms. vol. in mls. used, mls.kindgnt gms. mgs. solvent ugr9s ;;0 gl n w" 190 Pf. ethanol- 25 Br -200.686 8,524 1.155 Tartaric acid-10 gms. sucrose-10 Den. ethanol-90 10 1-25 .675 9,520 1.300

gms. Ethyleneglycol-l0,+malicacidl0, Den. ethanol-85 15 1 -20 .640 8,8461.200

+sucrose-5 Sucrose-20 Den. ethanol- 20 Br -20 .650 7,266 0.984Sucrose-20.... Den. ethanol-85.. l5 Br 20 .646 6,302 .854 lnvertsugar-'20 Methanol-90... 10 1 -20 .595 7,448 1.009Glucose-10,+glycerol-l0. Methanol-85... 15 Br 20 .584 7,260 .984Sucrose-20.. lsopropandl-SS... 15 1 -20 .573 7,691 1.042 Sucrose-21..nbutano190 10 1 -20 .637 8.363 1.133 Ethylene glyc lsoamyl alcohol- 10 l20 .618 8,188 1.109 Ethylene glycol-20 Den. ethanol-30 methanol-30 10 1-20 .769 8,785 1.190

+isopropanol30. l2 Ethylene glycol-20 Den. ethanol-80 10 1 -20 .6448,812 1.194 Ethylene glycol20... Den. ethanol-80.... 10 Br -20 .7348,426 1.142 Glycerol-15 Den. ethanol-75 10 Br -20 .641 8,010 1.085Mannitol-ZO Methanol45+2 butano1-45 10 1 -20 .617 8,467 1.148Molasses-20 (89 Brix) Den. ethanol-40+isopropanol40... 20 Br 20 .6667,892 1.069 Glycerol-10+tartaric acid-10.. Methanol-85 15 1 -20 .6418,018 1.086 18 Malic acid-20 Methanol-30+isopropanol-30+2 10 1 -20 .5999,313 1.262

amyl-30. i l glycol-.5 sm g-. .1299.- 9919 917315+" ?l@119lf35-;;1:: 202-2 8682 L176 erythritol-IO. 20 Ethylene glycol-l0+glycerol10..... 10 Br20 .638 8,214 1.1 13

Den. ethanol-40 benzyl alcohol NOTE: Den. ethanol equivalent to SDAFormula 1 (5 gal. wood alcohol added to every gals. ethyl alcohol) Pf.Ethanol equivalent to Grain alcohol-95% C H OH.

In the practice of this invention it is proposed that the solvents asoriginally prepared in their so-called concentrated form may be used forthe dissolution of gold metal per se. In instances where theconcentration of gold contained in the gold containing material to beprocessed is very low, a very dilute form of this solvent may be used.In such instances the gold may be both in physical or in chemicalcombination with other chemical elements such as for example ionic goldpresent in compounds such as gold sulfide, gold hydroxide, goldthioglucose, alloys, elemental gold and ionic gold as either or both maybe present in mineralized substances so called complexed and chelated"gold as present in organic compounds, ionic and colloidal gold aspresent as adsorbed gold, inorganic or organic salts or as adsorbed bycertain clays, activated silica and activated carbon in the form ofcolloidal particles of micron sized elemental gold, and in inorganic andorganic gold compounds which may be present as such or entrained,encased ro occluded in physically bound matter associated with humicacids and the like, e.g., including gums, resins, waxes, and soapsoccurring naturally in forest litter, and in certain known marinegeological deposits.

These new compositions of matter having utility as gold solvent systemsare characterized by their strong acidity, their content of availableand chemically reactable halogen, their ability to undergo hydrolysisand ionization, their content of water soluble halogenated andnon-halogenated organic compounds, their content of solvents capable ofdissolving materials such as gum, resins, and the like. They are furthercharacterized by their gold dissolving capabilities and their liquidstate. All these characteristics among others acting in concert allowthe solvents to be highly active not only with metallic gold but alsowith many other metals such as for example copper, silver, zinc,aluminum, and metals alloyed with gold. Additionally, their content oforganic alcohols, acids, esters, ketones and aldehydes present as bothhalogenated and non-halogenated compounds make these solvents capable ofdissolving a tremendous host of substances containing gold metal andcompounds of gold far beyond those cited above. The solvation ischaracterized in that the gold content of such solubilized matter joinsin chemical union with the compounds of the solvents to permit the quickand to the flask which was heated until its contents started to boil andthe vapors that formed returned to the flask as liquid condensate.Heating of the flask and contents was continued until it was noted thatthe vapor above the liquid was colorless and that the condensing vaporswere a light amber color. The flask and contents were removed from theheat source and allowed to cool to ambient temperature after which thecondenser was re moved momentarily to permit the addition of householdaluminum foil weighing approximately 1 gram. The flask and contents withreattached condenser were again heated until the contents were boiling.The heatready mechanical separation of such solvents pregnant with goldfrom unwanted and insoluble detritus. And further, due to the extremedegree of water solubility of all of the components of the vast numberof such gold solvents that can be prepared by the use of any of themajority of known water soluble saccharides, carboxylic acids,polyhydric alcohols, and monohydroxy alcohols and because of the nearlyinfinite range of dilutions of the solvents with water, it is possibleto prepare an infinite variety of gold metal solvents possessing aselective and wide variation of reactivities at extremely low costs. Thefollowing are examples illustrating some of the embodiments of thisinvention.

EXAMPLE I Ten grams of table sugar (sucrose) were dissolved in fifteenml. of water in a glass flask adapted for use with a water cooled refluxcondenser. Ten grams of ethylene glycol, 10 grams of elemental iodine,and 85 ml. of grain alcohol (190 Pf.) were added to the flask containingthe sugar solution. A reflux condenser was attached ing was continueduntil the liquid lost its red coloration and became colorless andtransparent after which the flask and contents were allowed to cool toambient temperature. Ten grams of elemental iodine were added anddissolved in the liquid in the flask to produce the gold metal solventwhich was used in the following manner as described in Examples IIthrough V.

EXAMPLE II In the first example of usage of the solvent prepared asdescribed above an accurately weighed amount of pure gold metal (99.99percent pure) in the amount of 10 grams of a fineness ranging between0.010 inch and 0.025 inch were placed in a clean, glass stoppered bottleafter which all of the gold solvent prepared other than I ml. was placedin the same bottle with the gold. The bottle was stoppered andmechanically shaken for 1 hour at ambient temperature after which theundissolved gold present was mechanically separated from the goldpregnant solution and washed free of gold pregnant liquid with severalsmall portions of grain alcohol, then dried, heated to red heat, andweighed. The

weight of recovered, isolated, insoluble gold metal whose chemicalpurity was determined to be equivalent to that of the original goldmetal exposed to treatment with the gold solvent was 0.82462 grams.

EXAMPLE III A piece of household aluminum. foil (approximately 2 inchesX 6 inches in size and weighing approximately 1 gram was added to theisolated gold pregnant solution (from above) after which the liquid withfoil was heated to and held in a temperature range of l30-l50F. toaccelerate displacement of the gold from its solution which requiredapproximately 1 hour of time. When it was noted that the liquidcontaining the aluminum foil had become colorless it was separatedmechanically from the insoluble solid matter present and reserved forre-halogenation and re-use. The insoluble solid matter present (goldfoil) was washed free of mother liquor with'small portions of grainalcohol with the washings being combined with the previously separatedgold-free mother liquor. The insoluble solid matter recovered was freedof alcohol by being gently heated to effect v-olatilization of suchalcohol after which the insoluble matter was digested with 10 ml. of anaqueous solution of nitric acid (approximately 35% HNO to effectdissolution of the residual aluminum foil. The nitric acid insolublematter was mechanically separated from the nitric acidaluminum nitratesolution and washed with distilled water to free it of any slat and acidcontaminants. The insoluble matter was then dried, heated to red heat,cooled, and weighed. The weight of recovered nitric acid insolublematter whose chemical composition was shown to be 99.97% Au was 9.17538grams. Thus the solvent dissolved 91.73% of the gold metal processedtherewith.

EXAMPLE IV In the second example of usage of the concerned solvent, the1 ml. of solvent reserved (as noted above) was diluted with water to avolume of 250 mls. and this aqueous solution was placed in a stopperedbottle with 296.7 grams (representative of a 10 assay ton sample of ore)of a gold-bearing pulverized ore known by fire assay analysis to contain0.90 troy ounce of gold per ton of ore, or containing the equivalent of0.90 mgs. Au per 29.67 grams of ore. The bottle with contents wasmechanically shaken for a time period of one hour after which theinsoluble solid portion was mechanically separated from the liquidportion and washed free of any occluded liquid which was combined withthe originally isolated mother liquor. The insoluble solid residue wasdiscarded. A piece of household aluminum foil (approximately 2 inches X2 inches and weighing approximately one-third gram) was placed in theisolated liquid which was then heated to and held in a temperature rangeof lO-l 25F. until the liquid became colorless. The aluminum foil in onepiece was removed from the liquid which was discarded. The aluminum foilwas washed with distilled water, placed in a glass beaker and treatedwith aqueous nitric acid solution (approximately 30% HNO and digested tocomplete dissolution of the aluminum foil. The acid insoluble residuewas mechanically separated from the nitric acid solution and washed freeof acid and soluble nitrate salts with water after which it was dried,heated to red heat, cooled, and weighed. The weight of recovered nitricacid insoluble solid matter was 0.01014 grams and by chemical analysiswas shown to consist of a combination of 84.7l% Au and 15.09% silica(SiO and 0.20% unidentified matter. 84.71% gold (Au) represents theequivalent of 0.00859 grams of gold per se to represent solvation andrecovery of 95.44% of the Au content known by fire assay analysis.

EXAMPLE V In the third example of usage of the solvent prepared asdescribed above, after the original solvent was used in the firstexample and stripped of its gold, it was reserved. In this example thisreserved solution was used as follows: Five grams of elemental iodinewere added to and dissolved in the previously used and recoveredsolvent. in turn this re-halogenated solvent was used in an identicalmanner as the predecessor was used in the first example cited aboveexcept that 5 grams of pure gold metal (99.99% Au) were processed. Theweight of undissolved gold metal was found to be 0.00551 grams, whilethe weight of dissolved and recovered gold was 4.99406 grams whichrepresents 99.89% of the gold metal processed. After the gold had beenstripped from this solution by use of aluminum metal foil as previouslydescribed and the gold-free solution had been separated from the goldand residual aluminum, this solution was re-used after adding anddissolving five grams of elemental iodine in the solution for treating agold alloy. This gold alloy consisted of one piece of metal having aweight of 7.20122 grams consisting of a gold content of 91.66% Au, asilver content of 4. l 6% Ag, and a copper content of 4.18% Cu. Thealloy and the solvent were shaken for a time period of 1 hour afterwhich the undissolved piece of alloy was removed, washed free ofsolvent, dried, and weighed to show a weight loss of 0.79487 grams. Thesolution was pro cessed in the same manner as were the previouslyprocessed gold pregnant solutions in the above examples and the amountof gold recovered as metal and determined to be 99.98% pure Au was0.72820 grams which represents about 99.95% of the weight of goldpresent in the portion of the alloy that was dissolved by the solventemployed in the processing.

C. Essentially Non-Aqueous Gold Solvating Systems Comprising SecondaryAlcohols and Iodine This family of gold solvation agents is particularlyadapted for treating gold bearing sedimentary rocks composed primarilyof limestone and sandstone containing both organic and inorganiccompounds of gold in addition to very finely divided elemental gold incombination with activated carbon and silica, to effect the solvationand recovery of the gold content of same.

The sedimentary rock referred to above is obtainable from the extensivedeposits of known gold bearing calcareous-carbonaceous rock. Thesecalcareouscarbonaceous gold bearing ores may be treated with thesolvents of this group whose primary purpose is to both dissolve andhold in the solution the organic and inorganic compounds present inthese types of ores while simultaneously converting the content of theores into organic and inorganic gold compounds which are similarlysoluble in the same liquid medium. After dissolution of the gold presentin the gold bearing material the gold pregnant liquid phase may beisolated mechanically from the unwanted, gold-free insoluble solid phasewhich is discarded. The isolated, gold-pregnant liquid may be treatedfor removal and recovery of its content of gold in the form of elementalgold. Thereafter the gold freed liquid may be re-employed in processingof similar types of gold-containing ores.

This class of gold solvents is uniquely adapted to overcome certainproblems inherent in and imposed by the nature of the materials soughtto be processed and the state of the gold therein contained. Theprincipal problem involves the fact that the gold content of such goldbearing ores may be in chemical combination with various organic acidsand hydroxy-compounds, such compounds including sulfur-containing typesas well as the those not containing sulfur. The gold may also be incombination with other organic or inorganic compounds. Additionally,gold may be present in elemental form, adsorbed on polar silica and onnon-polar carbon. Heretofore it has been impossible to achieve theseparation, isolation and recovery of all or even a major portion of thegold contained by such ores by the use of any known processes. Largeamounts of lime and alkali present in these ores cause such ores toexhibit high alkalinities upon exposure to water treatment. For example,one part by weight of a typical ore diluted with ten parts of water in asystem measured a pH greater than 9. Furthermore, water treatment causesthe formation of alkali stabilized hydrophilic and hydrophobic colloidsols which do not lend themselves to treatment by any known process forremoval and recovery of their total gold contents. Another problem isposed by the fact that the organic matter present in addition toactivated carbon and activated silica causes such ores to exhibit notonly great readiness for reduction but also high adsorptive capacity,rendering conventional processing such as by cyanidation completelyuseless for recovery of more than small percentages of the goldcontained by such ores.

The above problems are overcome by employing the solvent systems of thisinvention which may be characterized as non-aqueous and which by theirchemical nature are adapted to hold in solution iodine which is capableof chemically reacting with elemental gold. Fur thermore, thenon-aqueous solvents herein proposed are capable of displayingproperties of both a polar and non-polar solvent. Such solvents are notonly capable of wetting" the surfaces of both the polar silica and thenon-polar carbon present in the ore, but also, during the process ofsuch wetting their content of elemental and ionic iodine is brought intointimate contact with the absorbed gold and gold compounds on thesurfaces of the silica and the carbon, permitting combined chemical andphysical reactions to take place enabling the removal of both gold andgold compounds from the concerned surfaces in solubilized form.Additionally, such non-aqueous solvents are capable of dissolving gums,waxes, fats, resins and the like present in the ores to free any goldthat they might contain thereby allowing the iodine and iodine compoundspresent to effect the solvation of such gold into soluble gold iodinesalts. Further, such solvents are capable of holding in solution all ofthe gold compounds thus formed as the products of the reactions betweenthe iodine and iodine compounds of the solvent and the gold compoundspresent in the ore naturally.

The principal compound of the solvents of this invention comprisessecondary aliphatic alcohols such as for example isopropanol containinga quantity of dissolved elemental iodine. The process involvesessentially intimately admixing a gold-bearing material such as mine runore which has been ground to a fineness of approximately 90 percentminus 200 mesh US. Standard sieve size or finer to the action of thesolvent. During the ex posure the pulverized ore is mechanicallyagitated for a time period ranging between 2 to 3 hours and thereafterthe liquid phase is mechanically separated from the insoluble solids.The remaining solids are washed free of the gold-pregnant alcohol-iodinesolution with small portions of additional secondary alcohol containingtrace amounts (0.01% to 0.001%) of dissolved elemental iodine. Thewashings obtained are combined with the main body of previouslyseparated gold-pregnant solution. These gold pregnant solutions may thenbe processed as will be fully described below to separate and recovertheir contents of gold from the solvent system comprising iodine andsecondary alcohol.

It has been found that gold recovery can be greatly enhanced bysubjecting the mine run ore after it has been pulverized to fineness(where 90 percent or more is minus 200 mesh US. Standard Sieve size) tomoderate heating to a dull red heat in the range of 450 600 C. Thefunction of the temperature is for the primary purpose of removing bothfree water (moisture) and bound water (water of hydration). Such heattreatment appears to permit the exposure of far greater numbers ofdehydrated crystal faces of silica to the physical wetting and chemicalcombination when brought into contact with the secondary alcohol-iodinesolutions thus enhancing the degree of recovery. At the same time,deactivation of both the activated silica and the activated carbonappears to take place with the removal of bound hydroxyl groups,reducing and almost eliminating the tendency of these compounds of theore to form either lyophilic or lyophobic colloid sols upon exposure tothe iodine-secondary alcohol solvent while at the same time permitting acombination of physical solvation and chemical reaction to take placewith the gold and gold compounds present on the hydroxyl-free crystalfaces of silica and carbon. The relatively low temperature of heating ofthe pulverized ore prevents the occurrence of physical or chemical lossof elemental gold or gold compounds such as would occur in the case ofhigh temperature calcination processing. Some degree of oxidation doesoccur during the mild heating but such oxidation does not adverselyaffect the later dissolution and removal of the elemental gold and goldcompounds present in the ore so processed. It is there fore unnecessaryto provide a special atmosphere and the heating may be carried out undernormal atmospheric conditions.

After the ore has been heat processed and cooled to ambient temperatureit is ready for processing with the secondary alcohol-iodine solution inthe same manner as was described above for processing the mine-run,non-heat treated ore. In this connection it may be noted that thenon-heat treated pulverized ore permits a recovery of approximatelypercent of the total gold content of the ore while the heat treatingstep makes it possible to recover essentially all of the gold containedby these types of ores.

The use of elemental iodine is the preferred embodiment over the use ofany other halogens such as bromine or chlorine. The choice of alcohol tobe used in this process is critical. It has been found that the normalaliphatic alcohols such as e.g., methyl, ethyl, propyl, butyl, and amylhaving a content of elemental iodine of the same order as employed withsecondary alcohols such as isopropanol exert solvation power whichincreased with the number of carbons in their chains up to n-butanolafter which decreased solvation was noted to occur. However, in no casewas any singular primary alcohol or any mixture of such containingdissolved halogen whether elemental iodine or any other halogen capableof dissolving more than approximately 25 percent of the gold determinedby chemical analysis to be present in the ore processed. However,solvent systems comprising secondary aliphatic alcohols such asisopropanol, secondary butanol, and secondary amyl alcohols, whetherused singularly or in admixture, and regardless of which of the halogens(e.g., iodine, bromine, or chlorine) were present in solution were foundto have greater dissolving power than solvents based upon the primaryaliphatic alcohols. Of the secondary aliphatic alcohols tested, thetests indicated that isopro panol was the most suitable in thepreparation of iodine containing solvent systems for dissolving themajor portions and in some cases all of the gold and the gold compoundspresent in the ores processed with such. Additionally, isopropanol isreadily available as an anhydrous alcohol at reasonable cost and has thelowest boiling point (824 C.) of any of the secondary aliphatic alcoholsas well as having the highest evaporation rate of these alcohols thuspermitting its ready recovery by volatilization. Thus, the use ofisopropanol is noted as the preferred embodiment of this process overthe use of any other secondary aliphatic alcohol either singularly or inadmixture with other secondary alcohols.

The amount of elemental iodine found to be optimal for use in processingthese type ores was determined to be in the range between three and fivepounds of l per each ton of ore processed. The amount of isopropanol(anhydrus) found to be optimal for use in this process was determined tobe in the range of 180 to 200 gallons per each ton of ore underprocessing. However, since this process permits recovery of practicallyall of the isopropanol introduced and the major portion of elementaliodine used, the amount of either of these chemicals employed is notcritical beyond the requirements that there should be sufficientisopropanol present so that the ore under processing is completelywetted. Furthermore, the resultant ore-alcohol system should be of suchviscosity as to permit its being easily and completely mixed by the useof conventional mixing equipment. A rule of thumb formula for a suitablesystem is the combination of approximately equal parts by volume ofisopropanol containing the dissolved iodine and of pulverized ore of afineness as previously designated. There should be sufficient elementaliodine dissolved in the isopropanol used to insure ample iodine forreaction with gold and the gold compounds of the ore, plus a slightexcess.

The amount of iodine required to be used can be most easily ascertainedby processing sample lots of the ore concerned with portions ofisopropanol, each portion containing varying amounts of elemental iodineto pinpoint optimums. Experimental studies of several ores have shownthat, without exception they all were freed of more than 95 percent oftheir chemically ascertained content of gold by use of amounts ofisopropanol and elemental iodine dissolved in 180 gallons of isopropanolfor processing one ton (2,000 lbs.) of ore. The following is a classicexample of the use of this family of gold solvents.

EXAMPLE VI 296.7 grams of a pulverized (90 percent 200 mesh)calcareous-carbonaceous gold-bearing ore showing a gold content as Au of15.2 P.P.M. by atomic adsorption assay methods after first being heatedto a temperature of 600 C. then cooled was mixed for a two hour timeperiod by stirring with 250 mls. of anhydrous isopropanol containing 0.6grams of dissolved elemental iodine (1 After the mixing was done theresultant mixture was filtered and the insoluble solid residue waswashed on the filter with small portions -20 mls.) of anhydrousisopropanol containing 0.005 grams of dissolved elemental iodine pereach 100 mls. of the alcohol. The filtrate and combined washings wereheated to cause almost total evaporation of the isopropanol which wascaught as a liquid condensate and reserved for re-use. Thenon-volatilized residue almost completely free of isopropanol wascombined with about 50 mls. of water and heated to boiling after which apiece of household aluminum foil weighing approximately 0.5 grams wasadded. The aqueous solution with the aluminum foil was heated furtheruntil the solution became colorless and its content of gold becameattached to the foil. which was then removed from the gold-free aqueoussolution. The aqueous solution, after evaporation of its water left aresidue that upon acidification with a small quantity of concentratedsulfuric acid effected the liberation of its iodine from the iodidesalts present to leave as a collectible sublimate of elemental iodinereserved for re-use. The aluminum foil with its deposit of gold wasdissolved by use of an aqueous solution of nitric acid (approximately30% HNO to leave a residue of insoluble, elemental gold metal which wasmechanically isolated by filtration, washed free of acid and nitratesalts, dried, ignited to red heat, cooled, and weighed to show a weightof 4.62 mgs. whose chemical analysis showed it to contain 4.35 mgs. ofgold representating 4.35/4.4l or 98.65 percent of the gold shown to bepresent in the amount of ore processed.

EXAMPLE VI] A second sample of ore in the same amount as used above wastreated in identical manner in-as-far as removing the gold from the oreby use of the isopropanolcontaining iodine solvent. However, instead ofdisplacing the gold with aluminum as described above, the residueobtained from vaporization of the isopropanol was treated directly witha small amount of concentrated sulfuric acid (98.5% H SO to causedecomposition of the iodine compounds and liberation of crystals ofsublimed iodine which was trapped for re-use. Next, the iodine-free acidsystem was heated as is conventionally done in the parting of silver andother base metals from gold metal to free it of any contaminants afterwhich the isolated gold metal was heated to redness, cooled, and weighedto show a weight of 4.88 mgs. of which 89.95% was gold metal (4.39 mgs.)representing a recovery of 99.55% of the gold previously shown to bepresent in the ore processed. The contaminating 10.04% present was foundto be silica (SiO whose removal was effected by treating the residuewith hydrofluoric acid.

What is claimed as new is as follows:

1. A process for the separation and recovery of gold and/or compounds ofgold from substances containing same, which comprises:

a. finely dividing said gold or gold-compound containing substance;

b. subjecting said finely divided gold or gold compound containingsubstance by intimately admixing said substance with a gold solvationsystem consisting essentially of:

i. at least the stoichiometric quantity of dissolved elemental halogenrelative to the gold to be solubilized, said halogen being selected fromthe group consisting of iodine, bromine and mixtures thereof;

ii. at least sufficient alcohols selected from the group consisting ofprimary and secondary mono-hydroxy alcohols to solubilize the halogenpresent;

iii. a quantity of dissolved organic compounds relative to halogen inthe range, by weight, from about 1:4 to 1:], said dissolved organiccompounds being selected from the group consisting of saccharides,hydroxy carboxylic acids, diand polyhydric alcohols and mixturesthereof; and

iv. at least sufficient water to solubilize the quantity of saiddissolved organic compounds present; to form a gold-pregnant solutioncomprising dissolved gold compounds and an insoluble residuesubstantially free of gold;

c. separating said gold-pregnant solution from said insoluble residue;

d. recovering the gold content from the said goldpregnant solution.

2. The process of claim 1 wherein the said dissolved organic compound isa polyhydric alcohol.

3. The process of claim 1 wherein the saccharide utilized in the saidsolvent is sucrose.

4. The process of claim 1 wherein the halogen utilized in the saidsolvent is iodine.

5. The process of claim 1 wherein at least a portion of the water,primary and secondary mono-hydroxy alcohols, saccharides and carboxylicacids are supplied by an alcoholic beverage selected from the group ofdistilled alcoholic beverages, undistilled alcoholic beverage fermentsand mixtures thereof.

6. The process of claim 5 wherein the solvent is additionally fortifiedwith ethanol and sucrose.

7. The process of claim 1 wherein the saccharides are selected from thegroup consisting of mono-, diand polysaccharides and mixtures thereof.

8. The process of claim 1 wherein the carboxylic acids are selected fromthe group consisting of monodiand polyhydroxy mono and dicarboxylicacids and mixtures thereof.

9. The process of claim 1 wherein said solubilizing step includesagitating said solvent.

10. The process of claim 1 wherein said halogen does not exceed anexcess of percent over the stoichiometric requirements.

11. The process of claim 1 wherein the said solvent is prepared bydissolving the noted ingredients and heating same under reflux until theliquid condensate is slightly yellow indicating that the halogenemployed has combined chemically with the solution.

12. The process of claim 1 wherein the process for recovering the goldcontent of the said gold pregnant solution comprises:

a. placing a quantity of non-noble metal selected from the groupconsisting of: silver, copper, iron, zinc and aluminum into the saidgold-pregnant solution,

b. heating the said solution until the gold contents have becomesubstantially displaced from the solution and are found adhering to thenon-noble metal or as a free metal on the bottom of the vessel employed,and

c. removing the solvent freed of its gold contents leaving a solid goldcontaining residue.

13. The process of claim 12 wherein the non-noble metal employed fordisplacement of the noble metal is aluminum in sheet form.

14. The process of claim 12 wherein the solvent which has been freed ofits contents of noble metal is thereafter fortified with elementaliodine and is adapted to be re-used for solvation of gold fromsubstances containing same.

15. The process of claim 12 wherein the solid gold containing residue,after being separated from the solvent, is thereafter sequentiallysubjected to the following steps:

a. washing free of any remaining gold pregnant solution with a freshportion of solvent,

b. moderate heating to volatilize residual solvent,

0. treating with aqueous nitric acid solution to dissolve the non noblemetal residue,

d. separating said nitric acid insoluble gold metal residue, and

e. rinsing said gold metal residue with water to remove contaminatestherefrom.

16. A process for the separation and recovery of gold and/or compoundsof gold from particulate materials containing the same which comprisesintimately admixing a particulate material containing gold and/or goldcompounds with an essentially non-aqueous gold solvation system, saidsystem consisting essentially of an aliphatic secondary alcohol solutioncontaining at least the stoichiometric quantity of dissolved elementaliodine to dissolve the gold and/or gold compounds from said materialinto said solution; separating said solution from said material; andrecovering the gold content from said solution.

17. The process of claim 16 wherein the said alcohol is isopropanol.

18. The process of claim 16 which includes the step of subjecting minerun ore after it has been pulverized to a fineness where percent or moreis minus 200 mesh U.S. standard sieve size to moderate heating to a dullred heat in the range of 450 C. to-600 C.

2. The process of claim 1 wherein the said dissolved organic compound is a polyhydric alcohol.
 3. The process of claim 1 wherein the saccharide utilized in the said solvent is sucrose.
 4. The process of claim 1 wherein the halogen utilized in the said solvent is iodine.
 5. The process of claim 1 wherein at least a portion of the water, primary and secondary mono-hydroxy alcohols, saccharides and carboxylic acids are supplied by an alcoholic beverage selected from the group of distilled alcoholic beverages, undistilled alcoholic beverage ferments and mixtures thereof.
 6. The process of claim 5 wherein the solvent is additionally fortified with ethanol and sucrose.
 7. The process of claim 1 wherein the saccharides are selected from the group consisting of mono-, di- and polysaccharides and mixtures thereof.
 8. The process of claim 1 wherein the carboxylic acids are selected from the group consisting of mono- di- and polyhydroxy mono and dicarboxylic acids and mixtures thereof.
 9. The process of claim 1 wherein said solubilizing step includes agitating said solvent.
 10. The process of claim 1 wherein said halogen does not exceed an excess of 20 percent over the stoichiometric requirements.
 11. The process of claim 1 wherein the said solvent is prepared by dissolving the noted ingredients and heating same under reflux until the liquid condensate is slightly yellow indicating that the halogen employed has combined chemically with the solution.
 12. The process of claim 1 wherein the process for recovering the gold content of the said gold pregnant solution comprises: a. placing a quantity of non-noble metal selected from the group consisting of: silver, copper, iron, zinc and aluminum into the said gold-pregnant solution, b. heating the said solution until the gold contents have become substantially displaced from the solution and are found adhering to the non-noble metal or as a free metal on the bottom of the vessel employed, and c. removing the solvent freed of its gold contents leaving a solid gold containing residue.
 13. The process of claim 12 wherein the non-noble metal employed for displacement of the noble metal is aluminum in sheet form.
 14. The process of claim 12 wherein the solvent which has been freed of its contents of noble metal is thereafter fortified with elemental iodine and is adapted to be re-used for solvation of gold from substances containing same.
 15. The process of claim 12 wherein the solid gold containing residue, after being separated from the solvent, is thereafter sequentially subjected to the following steps: a. washing free of any remaining gold pregnant solution with a fresh portion of solvent, b. moderate heating to volatilize residual solvent, c. treating with aqueous nitric acid solution to dissolve the non-noble metal residue, d. separating said nitric acid insoluble gold metal residue, and e. rinsing said gold metal residue with water to remove contaminates therefrom.
 16. A process for the separation and recovery of gold and/or compounds of gold from particulate materials containing the same which comprises intimately admixing a particulate material containing gold and/or gold compounds with an essentially non-aqueous gold solvation system, said system consisting essentially of an aliphatic secondary alcohol solution containing at least the stoichiometric quantity of dissolved elemental iodine to dissolve the gold and/or gold compounds from said material into said solution; separating said solution from said material; and recovering the gold content from said solution.
 17. The process of claim 16 wherein the said alcohol is isopropanol.
 18. The process of claim 16 which includes the step of subjecting mine run ore after it has been pulverized to a fineness where 90 percent or more is minus 200 mesh U.S. standard sieve size to moderate heating to a dull red heat in the range of 450* C. to 600* C. 